Dry syrups, suspended in situ before administration, have conventionally been commercially available for anion exchange resin preparations which need a large dose. However, the dry syrups are inconvenient, because they take time for administration and require a large single dose. Some tablets have also been studied, however, no research has been made as for a relation between a size or a coating formulation of tablets and a property for easy take. Accordingly, a preparation that achieves higher compliance has been desired.
A tablet containing an anion exchange resin as a major component is required not to disintegrate in the mouth, but to rapidly disintegrate in the body so as to exhibit its efficacy. No published book describes what degree of non-disintegration in the mouth is sufficient. In a design for grains aiming at masking of unpleasant taste of a drug (PHARM TEC JAPAN, VOL. 6, No. 7, p 77 (1990)), practical sensory tests were employed by placing agents in the mouth for about 20 seconds and then spitting out the agents for evaluation with the purpose of prevention of the taste for 20 to 30 seconds. As for coatings of tablets containing an anion exchange resin as an active ingredient, a coating method is known wherein stearic acid is dissolved under heating in polyethylene glycol by using a cholestyramin resin without solvent (Japanese Patent Unexamined Publication (KOKAI) No. (Hei)3-236326). However, the resulting tablets has poor storage stability in open conditions. The tablet will disintegrate within several hours at room temperature, and accordingly, they have a problem of extremely poor stability after being unpacked. Further, the coating film has low strength and a high risk of wear and tear. Therefore, the tablets also have a problem that they suffer from breakage during packaging process or transportation.
In addition, a method is known in which a coating is performed using a solution of hydroxypropylmethylcellulose (Japanese Patent Unexamined Publication (KOKAI) No. (Hei) 7-97330). Tablets coated solely with celluloses will give sliminess due to dissolution of the celluloses on the surface of tablets in the mouth. When a tablet as a dosage has a large size, or several tablets are to be taken, the sliminess may not cause a direct problem in terms of a property for easy taking. However, when a single dosage comprises approximately 50 to 100 grains for easy taking of an anion exchange resin, which requires a large volume dosage, celluloses on the surface of the grain preparations will be dissolved to cause adherence and aggregation of the grain preparations in the mouth, which results in remarkable deterioration of feeling of taking.